1. Field of the Invention
The invention relates to a composition and method for preparing an automatic dishwasher detergent containing nonstaining bleach-sensitive dyes stabilized against decomposition from bleaching agents contained within the detergent formulation.
2. The Prior Art
Automatic dishwasher detergents are colored for identification. Confusion must be avoided between these detergents and other white granular products used in the kitchen. Avoidance of such confusion is desirable because dishwasher detergents necessarily are alkaline and contain a chlorine bleach. These components are hazardous when improperly used. They should not resemble such kitchen powders as sugar, salt, corn starch and other white granulates.
Yellow is a particularly attractive color. Several liquid dishwashing products on the market now contain lemon juice for extra cleaning power. Similarly, certain detergent powders contain a lemon scent. Lemon perfume pleasantly exudes from these powders. It would be incongruous, if not disappointing to the consumer, to color these powders other than yellow.
Those dishwasher detergents not marketed with a lemon theme frequently employ colors other than yellow. For instance, green is a particularly prevalent commercial color for these products.
While a wide choice of colorants is available for coloring the formulations, they are not all equally suitable. Generally, pigments are preferred because of their stability towards activated bleach, bleach being an important component in dishwasher detergents. Pigments suffer from one major disadvantage. They cause severe staining of plastic dishwasher parts and plastic tableware. In fact, for purposes of this disclosure, pigments are defined as plastic staining organic or inorganic chemicals. Illustrative of yellow colorants which stain are pigment Yellow Numbers 1, 3, and 49 identified by their Color Index (C.I.) numbers 11680, 11710 and 11765, respectively, and Yellow pigment 155. Colorants encompassed by this invention are herein defined as dyes. They are non-staining organic chemicals. They are almost always water-soluble for easy removal from substrates. However, there are some operative colorants suitable as dyes that may not be appreciably water-soluble
Staining can be overcome where special techniques are used to incorporate the pigment into the dishwasher formulation. For example, U.S. Pat. No. 3,544,473 to Kitchen et al teaches that insoluble phthalocyanine green causes severe staining when it is used with nonionic surfactants of the condensed propylene oxideethylene oxide variety. By utilizing a particular nonionic, a C.sub.13 -C.sub.21 fatty alcohol ethoxylated with 5-12 moles ethylene oxide, staining was eliminated.
Soluble dyes can be readily incorporated into dishwasher detergent formulations. They are preferable to pigments. They do not stain. Unlike the pigments, however, soluble dyes are frequently bleach-sensitive. For instance, chlorine from the chlorinating agent of a formulation may adversely interact with the dye. This causes color to fade or sometimes completely disappear.
It is an object of the present invention to provide a color stable automatic dishwasher detergent containing a bleaching agent and a bleach-sensitive dye.
It is a further object of this invention to present a method for obtaining color stable automatic dishwasher detergents containing a bleaching agent and a bleach-sensitive dye.